In the field of communications technologies, signals may usually be classified into two types: one type of signal carries information from a higher layer; the other type of signal does not carry information from a higher layer, and this type of signal is usually used for assisting in or indicating reception of the former type of signal. A transmit power of a signal is a very important parameter for both types of signals above. For example, a power of a reference signal may be used for deriving a path loss estimation value, and the path loss estimation value may be used as a part of open-loop control to implement uplink power control, or may be used as a basis for selecting a cell (or a transmit node, or a receive node). A power ratio of a physical downlink shared channel (PDSCH) signal to a reference signal (for example, a cell-specific reference signal (CRS) or a channel state information reference signal (CSI-RS)) may be used for deriving channel state information (CSI), thereby facilitating implementation of scheduling and link adaptation.
In existing Long Term Evolution (LTE) Releases R8-R11, a power-related parameter is determined on a base station side or a network side, and is notified to user equipment (UE) by using higher layer signaling. Because a conventional base station antenna configuration has a fixed downtilt, and an uplink and a downlink undergo similar path losses, so that a downlink path loss can be desirably used for estimating an uplink path loss. Therefore, distinguishing of antenna ports can be omitted in the power-related parameter sent by the base station side or the network side, and especially in a case of multiple antenna ports. If antenna ports are not distinguished, a downlink path loss can be desirably used for estimating an uplink path loss. The technology is desirably applicable to the conventional base station antenna configuration, especially if transmit powers of antenna ports are the same. In another aspect, a reference signal received power (RSRP), of a current cell/node or an adjacent cell/node, reported by user equipment (UE) may be used by a base station or an evolved node B (eNB) to select a serving cell or node for the UE. In the prior art, the RSRP is an estimation obtained by performing averaging on different antenna ports.
To lower a system cost and at the same time reach a higher system capacity and coverage requirement, active antenna systems (AAS) have been widely deployed in practice. At present, the LTE R12 standard that is about to be launched is considering enhancement of communication performance after introduction of an AAS system. Different from a conventional base station antenna, an AAS further provides design flexibility in a vertical direction of an antenna, where independent downtilts may be used in an uplink and a downlink, and powers of different antenna ports may be different. In addition, for AAS base stations, even if the AAS base stations have a same quantity of antenna ports, antenna array structures of the AAS base stations may also be different. Therefore, antenna ports having a same sequence number may also have different transmit powers in different array structures. In such a case, in the prior art, power control is implemented based on a downlink reference signal received power, or a method for selecting a cell/node is no longer effective. In the prior art, correct distinguishing cannot be performed if transmit powers of antenna ports are different, and a technical solution that accurately and effectively estimates an uplink path loss and estimates channel state information cannot be provided.